W2 P3: Classes and Scoped Enumerations

Question 1

Three class types:

Answer 1

class
struct
union

Question 2

True or False: a Subject class may include a data member of Subject* type

Answer 2

True

Question 3

True or False: a Subject class may include a data member of Subject type

Answer 3

False

Question 4

How to combine a class definition with the definition of one or more class instances:

Answer 4

class-key Identifier {

 sub-object declarations

 member function declarations

} identifier;

ex.
 class Subject {
     unsigned number;
     char desc[41];
 } subject, *pSubject;

Question 5

How to initialize a data member directly from the constructor definition:

Answer 5

Class-name(type x, …) : data-member-name{x},… { // any logic }

Question 6

What is an anonymous class

Answer 6

A class without a class name

Question 7

2 ways of defining an anonymous class:

Answer 7

// defining an instance of an
 // anonymous type (name)

 class Subject {
     int number;
     struct { // definition - no tag
         char shortName[7];
         char fullName[41];
     } identifier;
 }

or

// declaring a synonym type (Course)

typedef struct { // synonym - no tag
unsigned number;
char desc[41];
} Course;

Question 8

Prototypes for move constructors and move-assignment operators:

Answer 8

The prototype for a move-constructor takes the form

Class-name(Class-name&&);

The prototype for a move-assignment operator takes the form

Class-name& operator=(Class-name&&);

Question 9

Call move assignment operator:

Answer 9

class1 = std::move(class2)

Question 10

What is a class variable?

Answer 10

A class can include data members that hold the same information for all instances of the class and access that information regardless of the number of instances that currently exist. These are called class variables.

The keyword static declares a variable in a class definition to be a class variable.

ex.

unsigned Horse::noHorses = 0; // initializer

 class Horse {
     unsigned age;
     unsigned no;
 public:
     static unsigned noHorses;
     Horse(unsigned a);

Question 11

What is a class function?

Answer 11

A class function provides access to private class variables. The keyword static declares a function in a class definition to be a class function.

ex.
 class Horse {
     unsigned age;
     unsigned no;
     static unsigned noHorses;
 public:
     Horse(unsigned a);
     void display() const;
     ~Horse();
     static unsigned howMany();
 };

unsigned Horse::howMany() { return noHorses; }

Question 12

What is a union?

Answer 12

• Members are public by default
• members of a union share the same address
• can only hold the value of one member at a time

Question 13

What is an enumeration?

Answer 13

A type that holds a discrete set of symbolic constants.

• simplifies the readability and the upgradeability

ex.
enum Colour {white, red, green, blue};

std::ostream& operator